1. Field of the Invention
The present invention relates to a process for the removal of water soluble organic compounds from water. The invention further relates to a process for the removal of water soluble organic compounds associated with the production of crude oil. The invention further relates to a means of recovery of the soluble organic compounds present in produced oil field water.
2. Description of the Related Art
In the process of crude oil production from subterranean formations, a substantial amount of water may be produced. Such oil-associated water contains contaminating compounds which must be removed prior to releasing the water into the environment. For example, Environmental Protection Agency regulations currently stipulate a maximum oil content of 48 parts per million (ppm) for produced oil field water released into surface waters of the Gulf of Mexico and Pacific Ocean (Fed. Rep. 51, 24897, July 6, 1986).
Other sources of produced water are encountered in the refining of crude oil. Plants which process oil products are increasingly limited by federal and state regulations as to the total organic content (soluble and dispersed hydrocarbons) of effluent water. Additionally, certain production facilities such as steam-generation plants, typically require large amounts of deionized water for processing. Since shortages of freshwater routinely occur in semiarid and desert regions, facilities located in these areas must provide their own source of water.
Older techniques for dealing with contaminated water involved reinjection into wells or percolation through a series of treatment ponds. These methods were unacceptable due to their high costs and environmental damage. Even so, these techniques continue to be used where no economical options exist.
More modern methods of removing oil and water soluble organics from oil process water have been previously described. Canadian Patent 1,103,170 relates to the use of a macroreticular, cross-linked polymer adsorbent in columns capable of preferentially adsorbing oil. The patent further relates to the addition of pH adjusting agents coupled with a non-ionic surfactant to remove the adsorbed oil from the column. Additionally, the patent relates to the further alteration of the pH and to the final separation of the oil from the surfactant by phase separation techniques. The method taught by this patent, apart from including several intermediate steps in the purification and recovery process, has the disadvantage of requiring acidification during the processing thereby generating additional pollutants.
Two recent U.S. Pat. Nos. 4,818,410 and 4,839,054 relate to methods for removal of water soluble organics from produced water by acidification, mixing, and phase separation. Similarly to Canadian Patent 1,103,170, these methods include several intermediate steps in the purification and recovery process. Moreover, these patents relate to the use of strong acids, thereby adding pollutants to the process stream.
U.S. Pat. No. 4,775,475 relates to the removal of trace amounts of hydrocarbonaceous compounds from aqueous feedstreams by contacting the feedstream with a suitable adsorbent such as molecular sieves, amorphous silica-alumina gel, silica gel, activated carbon, activated alumina and clays. This patent relates further to the regeneration of these adsorbents by contacting with an elution solvent such as naphtha, kerosene, diesel fuel, gas oil or mixtures of these solvents. In further steps, this patent relates to the treatment of the hydrocarbonaceous compound and elution solvent admixture in the presence of hydrogen with a hydrogenation catalyst, further treatment with an aqueous scrubbing solution which preferably contains a strong base, and still further treatment by phase separation. The resulting spent aqueous scrubbing solution requires neutralization or other treatment prior to releasing into the environment.
One typical method utilized to overcome some of the adverse characteristics of the systems which generate additional pollutants is based upon activated carbon filtration. In an activated carbon system, the carbon must be routinely removed from the filter. After removal, the carbon is either regenerated outside the filter by heating to high temperatures or it is simply discarded and replaced with new material. Additional problems with activated carbon filters arise due to microbial growth on the carbon matrix itself.